Forensic Evidence: In Search of Justice

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I will never forget the time a Solicitor said to me: "It's fingerprint evidence, of course we always accept it!". He had obviously never heard of Andrew Chiory or Shirley McKie or Brandon Mayfield (the list could go on!) … have you?

We have learnt that it is vital for any evidence served to be examined. An Expert's duty is to the Court, to assist the Court with evidence within their expertise and be unbiased with the evidence they give. So, should we find we agree with another Expert, we will say so. However, we often find important facts have been ignored and have even found evidence to be completely wrong. We are not afraid to say that either!

• CCTV Evidence

What better evidence could you get than being able to see the offence happening and the person responsible? However, we are finding more frequently that the purported identifications of people from CCTV recordings are not as definitive as often alleged, and in some cases have been incorrect.

In one case in which the Defendant had been charged with a robbery on a bus, the Crown served a Police Officer's statement in which he identified the Offender seen in the CCTV footage as being the Defendant. Our Expert examined the original recording, found it to be of good quality and conducted a 'facial mapping' comparison between images of the Offender and photographs of the Defendant. Our Expert found that he could exclude the Defendant from being the Offender and the case was dropped.

In addition, it may not actually be possible to see specific actions take place, for example did a kick connect or multiple punches land on their target? CCTV footage is regularly 'over-interpreted' by those influenced by other information. Time-lapse video means that only a few images are recorded each second, for example only 6 images may have been recorded compared to 50 separate images per second for normal smooth motion. What is captured by those 6 images is chance and anything that happened in between is simply not recorded.

Furthermore, 'digital' does not necessarily mean better quality! Recordings are often compressed to help increase storage capacity, which usually reduces quality and can result in a 'blocky' image, obscuring fine detail and distorting shapes It can prove vital to have a report by an Expert who understands the limitations of CCTV recordings and states what can really be seen, so that the jury are not mislead.

• DNA Evidence

DNA is a chemical that is present in almost all of our body cells. It is the genetic material that governs the way we develop and determines our physical characteristics. We inherit half our DNA from our mother and half from our father.

For 14 years the 'SGM Plus' system was used by forensic laboratories for DNA testing. That method looked at 10 areas (or 'loci') on the DNA strand, plus the gender of the individual. At each of these loci there exist two lots of information (known as 'alleles' or 'components'), one inherited from each parent, meaning that a full SGM Plus DNA profile comprises 20 DNA components (i.e. 10 pairs), and an individual's gender identifier.

However, as more and more DNA profiles were added to the National DNA database, concern grew about the risk of finding two unrelated people with the same SGM Plus DNA profile. A new generation of DNA testing methods is therefore now in use that are known collectively as 'DNA17'. These more discriminating tests look at 16 areas on the DNA strand, plus a person's gender, meaning that a full 'DNA17' profile consists of 32 DNA components (i.e. 16 pairs) and gender, rather than the 20 components in an 'SGM Plus' profile.

We have therefore found ourselves in a crossover period, where there are thousands of DNA reference profiles from people on the National DNA Database that were produced using the SGM Plus method, whereas samples from crimes are now tested using a DNA17 system. This means that when a database 'hit' is obtained, the information from only a maximum of 10 loci (i.e. 20 components), plus gender, on a person's DNA profile is likely to have been matched to the DNA profile from the crime, from which there is potentially information from 16 loci (i.e. 32 components), plus the gender, available for comparison. There are therefore a potential 12 components from the crime sample that have not been compared with the person's DNA.

What if any of those 12 alleles do not match and the Defendant can be excluded from being the Offender?

It is therefore imperative that any DNA matches produced as a result of a DNA Database 'hit' are examined and, should it be found that the samples were profiled using systems that each look at a different number of loci on the DNA strand, new testing should be conducted using suitable methods to ensure all available evidence is considered.

Current DNA testing methods are also extremely sensitive and are able to obtain DNA profiles from tiny samples. It should always be borne in mind that whilst a full DNA profile may have been produced from a crime sample, the substance from which the profile was obtained may have been so small as to be invisible to the naked eye. For example, the 'DNA17' methods are thought to be able to produce a DNA profile from less than 10 skin cells, and it is estimated that a person sheds about 400,000 such cells a day! Methods of indirect deposition and secondary, and even tertiary, DNA transfer should not be forgotten!

Reporting methods have also evolved, with 'Streamlined Forensic Reports' (SFRs) often favoured by Police, especially when the evidence has been found as a result of a Database Hit. However, our Experts have discovered on several occasions that evidence produced in DNA SFRs has been wrong – alleged DNA matches with a supporting match probability have subsequently been found to actually be mixtures of DNA that are unsuitable for statistical evaluation!

• Crime Scene Examination and DNA Evidence

Quite often one type of evidence can have an impact on another. We were instructed in a case in which DNA obtained at a burglary scene was found to match the Defendant. The DNA had been swabbed from lip prints on the outside of a window that had been found by the Crime Scene Examiner when they powdered the crime scene looking for fingerprint evidence.

However, in an unusual set of circumstances, the Defendant had also been burgled and the same Police Crime Scene Examiner had attended the Defendant’s home to conduct an examination prior to attending the other burglary scene later that same day, and thus the question of contamination arose and our Crime Scene Examiner reviewed the evidence.

Based on information and questions raised by our Expert, the Crown’s Examiner admitted to Defence Counsel in a conference held at Court that he may have used the same fingerprint brush and powder at both crime scenes, and, because of research our Expert was aware of regarding the contamination of fingerprint brushes and powder with DNA, the Crown’s DNA Scientist confirmed that DNA could have been transferred via the fingerprint brush from the Defendant’s home to the other burglary scene. As a result, as the trial was about to start the Crown offered no evidence.

• Drugs Evidence

Police Forces have to take a practical view of forensic testing, especially with so many budget constraints. However, that can have a disastrous effect on evidence served.

In one case the Defendant had been charged with possession of cannabis with intent to supply and faced a 3 year prison sentence if convicted. The Police hadseized over 2kg of a bulky vegetable material that they suspected to be drugs, but in order to save costs they only submitted two very small samples of thematerial for forensic testing, claiming they were representative samples of the whole seizure. Their forensic service provider reported that the samples were "cannabis, including leaf material and some flowering top material" and the Police subsequently valued the entire seized material at £20,000, based on it being marketable cannabis that could have been sold on the street in 2000 'deals' at £10 each.

However, the Defendant was adamant that the cannabis was "rubbish" and his Solicitor asked our Expert to examine the material that had been seized. He found that it was nearly all cannabis plant stalk and leaf with only tiny fragments of (the potent) flowering tops present, and many clay pebbles (plant growing material) mixed with it. The Police samples had in fact been unrepresentative of the bulk material which was unmarketable and in our Expert's opinion, discarded waste material from a cannabis factory (where the marketable flowering tops had been separated out).

Our Expert's report resulted in the Police agreeing with his evidence and the Defendant receiving a £150 fine for cannabis possession, instead of a jail term forpossession with intent to supply a significant quantity of cannabis.

• Fingerprint Evidence

Fingerprints are still the only accepted unique method of identification (even identical twins have different fingerprints) and such evidence is retrieved in many cases, for example the Metropolitan Police find and retrieve finger/palm marks from approximately a fifth of all crime scenes attended by their Crime Scene Examiners. However, Police Forces have their set ways in producing their evidence (especially with the introduction of 'Streamlined Forensic Reports') and very limited information is readily given.

Our fingerprint expert was asked to examine the evidence produced by the Police in relation to the armed robbery of a jewellers shop. Latex gloves had been left at the scene, which were retrieved by the Police and subjected to a fingerprint examination. A finger mark made by the Defendant was said by the Police to have been found on the inside of one of the gloves. The Defendant had a legitimate reason for touching the outside of the latex gloves but not for wearing them.

Our Expert advised Counsel that there was no proof in the evidence served by the Crown that the mark was definitely found on the inside of the glove, particularly as latex gloves are often removed in a manner that causes them to be turned inside out. On cross examination the Police could not confirm if the mark was found on the inside or outside of the glove and the Defendant was found not guilty.

It is therefore not always about whether or not the finger (or palm) mark identification is correct, there are often many other important factors that can be brought to light.

• Toxicology

Toxicology evidence can arise in many different cases, including driving related matters, assaults, sex offences and murders, and can be thought of as difficult to dispute. Techniques used to analyse blood and urine samples are specific enough that there are rarely incidences where false positive results are obtained.

It is, however, important to view the results alongside all evidence in the case. Morphine is, for example, commonly used as a pain killer and if someone has been injured morphine may have been administered to them after an incident occurred. Its presence in the blood may not therefore show that an individual was under the effect of the drug at the time of the offence.

It is also important to consider the interaction that may take place between different drugs, which can result in an enhanced effect. Individual concentrations of each drug may not themselves cause significant effects, but if a number of drugs with similar effects are taken in combination, or if drugs are taken with alcohol, this may increase their effect on an individual. The medical history of a person can also prove important when interpreting toxicological findings as certain medical conditions can alter how an individual responds to a drug.

Drugs can also undergo post mortem re-distribution, so in the case of fatalities, the level detected after death may not be representative of the level in the blood at the time of death. Interpretation of post mortem levels therefore needs to take into account the time between death and sampling, the preservatives used and the temperature at which samples have been stored. Comparison of levels in different tissue samples, such as blood, stomach contents and vitreous humour can assist with assessing the extent of post mortem re-distribution that has taken place.

An examination of toxicology evidence can therefore be of paramount importance to many cases, as it may explain an individual's behaviour and reactions tocircumstances they faced, or actually show they were not under the effect of a drug at the time of the incident.

Instructing Experts

In the interests of justice, instructing an independent expert to examine evidence is vital. Evidence might not be as absolute as it seems, only limited information may have been disclosed in a report or the evidence could even be wrong. Forensic evidence should be fairly presented, to enable the Court to consider all relevant information and ensure they are not mislead by incomplete, or even incorrect, evidence.

I will never forget the time a Solicitor said to me: "It's fingerprint evidence, of course we always accept it!". He had obviously never heard of Andrew Chiory or Shirley McKie or Brandon Mayfield (the list could go on!) … have you?

We have learnt that it is vital for any evidence served to be examined. An Expert's duty is to the Court, to assist the Court with evidence within their expertise and be unbiased with the evidence they give. So, should we find we agree with another Expert, we will say so. However, we often find important facts have been ignored and have even found evidence to be completely wrong. We are not afraid to say that either!

• CCTV Evidence

What better evidence could you get than being able to see the offence happening and the person responsible? However, we are finding more frequently that the purported identifications of people from CCTV recordings are not as definitive as often alleged, and in some cases have been incorrect.

In one case in which the Defendant had been charged with a robbery on a bus, the Crown served a Police Officer's statement in which he identified the Offender seen in the CCTV footage as being the Defendant. Our Expert examined the original recording, found it to be of good quality and conducted a 'facial mapping' comparison between images of the Offender and photographs of the Defendant. Our Expert found that he could exclude the Defendant from being the Offender and the case was dropped.

In addition, it may not actually be possible to see specific actions take place, for example did a kick connect or multiple punches land on their target? CCTV footage is regularly 'over-interpreted' by those influenced by other information. Time-lapse video means that only a few images are recorded each second, for example only 6 images may have been recorded compared to 50 separate images per second for normal smooth motion. What is captured by those 6 images is chance and anything that happened in between is simply not recorded.

Furthermore, 'digital' does not necessarily mean better quality! Recordings are often compressed to help increase storage capacity, which usually reduces quality and can result in a 'blocky' image, obscuring fine detail and distorting shapes It can prove vital to have a report by an Expert who understands the limitations of CCTV recordings and states what can really be seen, so that the jury are not mislead.

• DNA Evidence

DNA is a chemical that is present in almost all of our body cells. It is the genetic material that governs the way we develop and determines our physical characteristics. We inherit half our DNA from our mother and half from our father.

For 14 years the 'SGM Plus' system was used by forensic laboratories for DNA testing. That method looked at 10 areas (or 'loci') on the DNA strand, plus the gender of the individual. At each of these loci there exist two lots of information (known as 'alleles' or 'components'), one inherited from each parent, meaning that a full SGM Plus DNA profile comprises 20 DNA components (i.e. 10 pairs), and an individual's gender identifier.

However, as more and more DNA profiles were added to the National DNA database, concern grew about the risk of finding two unrelated people with the same SGM Plus DNA profile. A new generation of DNA testing methods is therefore now in use that are known collectively as 'DNA17'. These more discriminating tests look at 16 areas on the DNA strand, plus a person's gender, meaning that a full 'DNA17' profile consists of 32 DNA components (i.e. 16 pairs) and gender, rather than the 20 components in an 'SGM Plus' profile.

We have therefore found ourselves in a crossover period, where there are thousands of DNA reference profiles from people on the National DNA Database that were produced using the SGM Plus method, whereas samples from crimes are now tested using a DNA17 system. This means that when a database 'hit' is obtained, the information from only a maximum of 10 loci (i.e. 20 components), plus gender, on a person's DNA profile is likely to have been matched to the DNA profile from the crime, from which there is potentially information from 16 loci (i.e. 32 components), plus the gender, available for comparison. There are therefore a potential 12 components from the crime sample that have not been compared with the person's DNA.

What if any of those 12 alleles do not match and the Defendant can be excluded from being the Offender?

It is therefore imperative that any DNA matches produced as a result of a DNA Database 'hit' are examined and, should it be found that the samples were profiled using systems that each look at a different number of loci on the DNA strand, new testing should be conducted using suitable methods to ensure all available evidence is considered.

Current DNA testing methods are also extremely sensitive and are able to obtain DNA profiles from tiny samples. It should always be borne in mind that whilst a full DNA profile may have been produced from a crime sample, the substance from which the profile was obtained may have been so small as to be invisible to the naked eye. For example, the 'DNA17' methods are thought to be able to produce a DNA profile from less than 10 skin cells, and it is estimated that a person sheds about 400,000 such cells a day! Methods of indirect deposition and secondary, and even tertiary, DNA transfer should not be forgotten!

Reporting methods have also evolved, with 'Streamlined Forensic Reports' (SFRs) often favoured by Police, especially when the evidence has been found as a result of a Database Hit. However, our Experts have discovered on several occasions that evidence produced in DNA SFRs has been wrong – alleged DNA matches with a supporting match probability have subsequently been found to actually be mixtures of DNA that are unsuitable for statistical evaluation!

• Crime Scene Examination and DNA Evidence

Quite often one type of evidence can have an impact on another. We were instructed in a case in which DNA obtained at a burglary scene was found to match the Defendant. The DNA had been swabbed from lip prints on the outside of a window that had been found by the Crime Scene Examiner when they powdered the crime scene looking for fingerprint evidence.

However, in an unusual set of circumstances, the Defendant had also been burgled and the same Police Crime Scene Examiner had attended the Defendant’s home to conduct an examination prior to attending the other burglary scene later that same day, and thus the question of contamination arose and our Crime Scene Examiner reviewed the evidence.

Based on information and questions raised by our Expert, the Crown’s Examiner admitted to Defence Counsel in a conference held at Court that he may have used the same fingerprint brush and powder at both crime scenes, and, because of research our Expert was aware of regarding the contamination of fingerprint brushes and powder with DNA, the Crown’s DNA Scientist confirmed that DNA could have been transferred via the fingerprint brush from the Defendant’s home to the other burglary scene. As a result, as the trial was about to start the Crown offered no evidence.

• Drugs Evidence

Police Forces have to take a practical view of forensic testing, especially with so many budget constraints. However, that can have a disastrous effect on evidence served.

In one case the Defendant had been charged with possession of cannabis with intent to supply and faced a 3 year prison sentence if convicted. The Police hadseized over 2kg of a bulky vegetable material that they suspected to be drugs, but in order to save costs they only submitted two very small samples of thematerial for forensic testing, claiming they were representative samples of the whole seizure. Their forensic service provider reported that the samples were "cannabis, including leaf material and some flowering top material" and the Police subsequently valued the entire seized material at £20,000, based on it being marketable cannabis that could have been sold on the street in 2000 'deals' at £10 each.

However, the Defendant was adamant that the cannabis was "rubbish" and his Solicitor asked our Expert to examine the material that had been seized. He found that it was nearly all cannabis plant stalk and leaf with only tiny fragments of (the potent) flowering tops present, and many clay pebbles (plant growing material) mixed with it. The Police samples had in fact been unrepresentative of the bulk material which was unmarketable and in our Expert's opinion, discarded waste material from a cannabis factory (where the marketable flowering tops had been separated out).

Our Expert's report resulted in the Police agreeing with his evidence and the Defendant receiving a £150 fine for cannabis possession, instead of a jail term forpossession with intent to supply a significant quantity of cannabis.

• Fingerprint Evidence

Fingerprints are still the only accepted unique method of identification (even identical twins have different fingerprints) and such evidence is retrieved in many cases, for example the Metropolitan Police find and retrieve finger/palm marks from approximately a fifth of all crime scenes attended by their Crime Scene Examiners. However, Police Forces have their set ways in producing their evidence (especially with the introduction of 'Streamlined Forensic Reports') and very limited information is readily given.

Our fingerprint expert was asked to examine the evidence produced by the Police in relation to the armed robbery of a jewellers shop. Latex gloves had been left at the scene, which were retrieved by the Police and subjected to a fingerprint examination. A finger mark made by the Defendant was said by the Police to have been found on the inside of one of the gloves. The Defendant had a legitimate reason for touching the outside of the latex gloves but not for wearing them.

Our Expert advised Counsel that there was no proof in the evidence served by the Crown that the mark was definitely found on the inside of the glove, particularly as latex gloves are often removed in a manner that causes them to be turned inside out. On cross examination the Police could not confirm if the mark was found on the inside or outside of the glove and the Defendant was found not guilty.

It is therefore not always about whether or not the finger (or palm) mark identification is correct, there are often many other important factors that can be brought to light.

• Toxicology

Toxicology evidence can arise in many different cases, including driving related matters, assaults, sex offences and murders, and can be thought of as difficult to dispute. Techniques used to analyse blood and urine samples are specific enough that there are rarely incidences where false positive results are obtained.

It is, however, important to view the results alongside all evidence in the case. Morphine is, for example, commonly used as a pain killer and if someone has been injured morphine may have been administered to them after an incident occurred. Its presence in the blood may not therefore show that an individual was under the effect of the drug at the time of the offence.

It is also important to consider the interaction that may take place between different drugs, which can result in an enhanced effect. Individual concentrations of each drug may not themselves cause significant effects, but if a number of drugs with similar effects are taken in combination, or if drugs are taken with alcohol, this may increase their effect on an individual. The medical history of a person can also prove important when interpreting toxicological findings as certain medical conditions can alter how an individual responds to a drug.

Drugs can also undergo post mortem re-distribution, so in the case of fatalities, the level detected after death may not be representative of the level in the blood at the time of death. Interpretation of post mortem levels therefore needs to take into account the time between death and sampling, the preservatives used and the temperature at which samples have been stored. Comparison of levels in different tissue samples, such as blood, stomach contents and vitreous humour can assist with assessing the extent of post mortem re-distribution that has taken place.

An examination of toxicology evidence can therefore be of paramount importance to many cases, as it may explain an individual's behaviour and reactions tocircumstances they faced, or actually show they were not under the effect of a drug at the time of the incident.

Instructing Experts

In the interests of justice, instructing an independent expert to examine evidence is vital. Evidence might not be as absolute as it seems, only limited information may have been disclosed in a report or the evidence could even be wrong. Forensic evidence should be fairly presented, to enable the Court to consider all relevant information and ensure they are not mislead by incomplete, or even incorrect, evidence.